Ordinary assembled units of the tube type, meaning an inner tube, consist of a wheel rim, which among other things comprises rim flanges, a tire, and an inner tube whose function is to retain the pressure and keep the tire on the rim. In the event of a puncture, these assembled units are simple to repair. A repair may consist in identifying the source of the leak of air and therefore a hole in the inner tube and sealing it with a repair patch. Such a repair is quite simple and can be done with very little experience. Another way is to replace the punctured inner tube with a new inner tube, provided the user has one available.
When the user is travelling and does not have either repair means or a replacement inner tube available, it is desirable for him or her to be able to return home or reach a repair place by continuing to travel without having to do anything directly to the assembled unit.
This scenario is particularly desirable for users who use a bicycle every day to go to work for example. This type of user is not usually dressed ideally and has not got time to set about repair work him or herself. Moreover, the complexity of certain bicycles, specifically the rear wheels with for example derailleurs built into the hub, often makes a repair a very difficult task.
Solutions have already been proposed to users to mitigate the inconvenience of this type of incident. Examples of these are solutions that limit the risk of puncture. For example, tires have been provided which comprise under the tread a thicker layer of rubber, or protective foams that form a barrier against potential punctures.
These solutions can certainly improve the situation but remain limited to preventing incidents affecting the tread. Punctures by perforations in the sidewalls of the tire cannot for example be avoided with this type of product.
Moreover, the comfort and performance in terms of rolling resistance are not equivalent to those of a normal tire.
The use of solid tires whose special feature of course is that they cannot be punctured has already been proposed. This type of solution is interesting but reduces the properties of comfort or wear and often complicates the fitting of the assembled unit.
Solutions relating to the inner tube have also already been proposed. Document U.S. Pat. No. 2,535,120 discloses for example an inner tube comprising raised forms consisting of humps on its outer surface which when the inner tube is pressurized inside an assembled unit limit or prevent the stretching of said surface or even keep a surface in compression. Thus, when an accidental perforation of the inner tube occurs, the condition of the surface produced in this way by the presence of humps causes the hole created by the perforation to be instantly “sealed”.
Tests done on inner tubes for assembled units designed for bicycles have shown that such a solution is of only relative efficacy, depending in particular on the location of the puncture in the surface of the inner tube.
Specifically, the inventors have demonstrated that the formation of the humps on a bicycle inner tube combines a toroidal surface with raised forms, having in particular a small radius of curvature, and, since the shape of said reliefs is defined identically for all of said reliefs, the connections between them and the toroidal surface vary depending on the particular location of said reliefs on the surface. As a consequence, certain connecting regions inevitably create regions of stretching, which explains the ineffectiveness of such an inner tube in certain cases where perforation occurs in said stretched regions. One solution which would consist in defining the profile of each hump based on its position on the toroidal surface could be used to avoid stretching certain connecting regions, but is out of the question from an industrial point of view.
There also exist devices that take the form of an aerosol and that allow a substance to be introduced into the inner tube to seal a puncture. These solutions, which can also be used preventively, are of course limited to certain types of minor damage to the tire and inner tube.
The circumferential direction of the assembled unit, or longitudinal direction, is the direction corresponding to the periphery of the assembled unit and is defined by the direction in which the assembled unit rolls.
The transverse or axial direction of the assembled unit is parallel to the axis of rotation of the assembled unit.
The radial direction is a direction that intersects the axis of rotation of the assembled unit and is perpendicular to it.
The axis of rotation of the assembled unit is the axis about which it rotates in normal use.
A radial or meridian plane is a plane containing the axis of rotation of the assembled unit.
The circumferential median plane, or equatorial plane, is a plane perpendicular to the axis of rotation of the assembled unit and which divides the assembled unit into two halves.